SPIN BOLDAK, AFGHANISTAN -- The pace of President Obama's troop buildup in Afghanistan hinges in part on a narrow, pothole-riddled dirt track that is controlled by a 33-year-old suspected drug lord and by the whims of the Pakistani military.

It is down this road each month that thousands of cargo trucks bearing U.S. and NATO military supplies pass through the only major border crossing in southern Afghanistan -- the area where most American troop reinforcements are scheduled to deploy.

Here at the border crossing, where traffic switches from the left side of the road in Pakistan to the right in Afghanistan, supply trucks must pass along with the flood of pedestrians, donkey carts, drug shipments and materials to make roadside bombs. Only about 2 to 3 percent of the vehicles are regularly searched, and payoffs to border guards are rampant, U.S. military officials say.

The chaos and congestion of this border crossing have become a matter of urgent concern as military logisticians scramble to fulfill Obama's plan for bringing 30,000 more U.S. troops to Afghanistan this year. Compounding the problem is that Pakistan has been slow to respond to U.S. proposals to create a separate lane for coalition military vehicles and nighttime crossing rights, U.S. officials say.

Gen. Stanley A. McChrystal, the top U.S. and NATO commander in Afghanistan, flew to Quetta, Pakistan, on Monday to meet with Pakistani military commanders, then toured the border crossing with officials from both countries.

"It's absolutely key to have this gate functioning better," said Maj. Gen. Hubert De Vos, a Belgian army officer who is the deputy chief of staff for resources with the coalition military command. "It's a direct link to the south, and the south is absolutely critical."

Hastening overland supplies of fuel, food and military equipment to Afghanistan is just one issue in a frenzy of logistical work that is required to feed, house and protect soldiers coming to fight. The military is rushing to construct and expand military bases, dig wells and build power plants, dining halls, aircraft landing strips and temporary housing. At the end of each week, coalition officials responsible for southern Afghanistan convene for hours to monitor the progress -- meetings that have earned the nickname "Friday night fights."

Maj. Gen. Don T. Riley, the chief engineer for U.S. forces in Afghanistan, said the pace of traffic through Spin Boldak needs to increase to 150 NATO supply trucks a day, up from the current average of just under 100. These additional trucks are needed, among other reasons, to slake the military's demand for fuel, which is expected to increase by 30 to 40 percent.

The U.S. military has longer-term plans to build a bypass road around the crossing. In the short term, it is pushing for overnight access through the border.

But for the past month, Pakistan has given little ground. Part of the problem is apparently bureaucracy, with at least five Pakistani agencies involved in providing security for NATO convoys between the port city of Karachi and the border. In the past, Pakistani officials also have criticized U.S. plans to increase troop levels, arguing that an intensified war will spread back into their country.

There is trouble on the Afghan side as well. The urgency to increase the flow of military supplies has forced the U.S. military to rely heavily on Abdul Razziq, the illiterate local commander of the Afghan border police.

According to U.S. military officials, Razziq wields near total control over Spin Boldak and the border crossing. Razziq, a former anti-Taliban fighter, owns a trucking company, commands 3,500 police, effectively controls the local government, and reportedly takes in millions from extorting passing vehicles and trafficking drugs. He is a colonel, but his soldiers call him "general." On Monday, Razziq popped pistachios while smiling and chatting with U.S. generals.